U.S. patent application number 11/585371 was filed with the patent office on 2008-07-17 for small diameter intravascular catheter with screw tip and limited torsional displacement.
Invention is credited to Jason Garrity, Dean Peterson, Howard Root, Jeff Welch.
Application Number | 20080172008 11/585371 |
Document ID | / |
Family ID | 39618334 |
Filed Date | 2008-07-17 |
United States Patent
Application |
20080172008 |
Kind Code |
A1 |
Root; Howard ; et
al. |
July 17, 2008 |
Small diameter intravascular catheter with screw tip and limited
torsional displacement
Abstract
A catheter to be passed over a guidewire, including a screw
portion with a cylindrical hollow shaft and a helical thread
portion extending outwardly from the hollow shaft. The screw
portion is secured coaxially to a tubular portion formed from a
substantially rigid material. The tubular portion has, along a
portion of its length, at least two slits having a pattern geometry
that limits torsional displacement. The catheter also includes a
hub having a lumen joined substantially coaxially to the tubular
portion.
Inventors: |
Root; Howard; (Excelsior,
MN) ; Welch; Jeff; (Maple Grove, MN) ;
Garrity; Jason; (Minneapolis, MN) ; Peterson;
Dean; (Rogers, MN) |
Correspondence
Address: |
PATTERSON, THUENTE, SKAAR & CHRISTENSEN, P.A.
4800 IDS CENTER, 80 SOUTH 8TH STREET
MINNEAPOLIS
MN
55402-2100
US
|
Family ID: |
39618334 |
Appl. No.: |
11/585371 |
Filed: |
October 24, 2006 |
Current U.S.
Class: |
604/264 |
Current CPC
Class: |
A61M 25/0069 20130101;
A61M 25/0068 20130101; A61M 25/01 20130101; A61M 2025/0059
20130101 |
Class at
Publication: |
604/264 |
International
Class: |
A61M 25/00 20060101
A61M025/00; A61M 5/00 20060101 A61M005/00 |
Claims
1. An intravascular catheter to be passed over a guidewire,
comprising: a screw portion including a hollow shaft defining a
lumen and a helical thread portion extending outwardly from the
hollow shaft; and a tubular portion formed from a substantially
rigid material, having a length, joined substantially coaxially to
the screw portion and defining a lumen that is continuous with the
lumen of the screw portion, the tubular portion including at least
two slits defined along at least some of the tubular portion, the
two slits having a pattern geometry that limits torsional
displacement of at least a portion of the catheter, the at least
two slits having a first end and a second end, the first end and
the second end being longitudinally displaced from one another
along the length of the tubular portion, wherein the lumen of the
screw portion and the lumen of the tubular portion are dimensioned
to pass over a guidewire.
2. The catheter as claimed in claim 1, in which the tubular portion
has a first diameter and the hollow shaft of the screw portion has
a second diameter and the first and second diameter are
substantially equal; the helical thread portion has a first
handedness and the slits are generally helical and have a second
handedness opposed to the first handedness; the slits are generally
helical and the generally helical slits further include sigmoid
curves that repeat along the length of the tubular portion with a
substantially regular periodicity; the tubular portion has a
diameter of about two French and further comprising an inner liner
and an outer coating; and a hub having a lumen joined substantially
coaxially to the tubular portion.
3. The catheter as claimed in claim 1, in which the helical thread
portion has an outside diameter significantly larger than the
second diameter of the hollow shaft.
4. The catheter as claimed in claim 3, in which the first diameter
of the helical thread portion is at least about one and one third
times the second diameter of the hollow shaft.
5. The catheter as claimed in claim 1, further comprising a torque
device couplable to the tubular portion whereby torque can be
applied to the tubular portion.
6. The catheter as claimed in claim 1, in which the pattern
geometry is such that torsional displacement is limited to a
greater degree in a first rotational direction than in a second
rotational direction.
7. A method of controlling flexibility and torsional displacement
in an intravascular catheter, comprising: forming a portion of the
catheter from a unitary tubular substantially rigid structure
having a wall and a length and defining a lumen; piercing the wall
with at least two continuous slits along a substantial portion of
the length of the wall, each slit having a first end and a second
end, the first end and the second end being longitudinally
displaced from each other along the length of the tubular
substantially rigid structure thereby imparting flexibility to the
tubular substantially rigid structure; and forming the slits with a
pattern geometry that limits torsional displacement of at least a
portion of the catheter.
8. The method as claimed in claim 7, further comprising forming a
helical thread portion at a distal end of the catheter that has a
first handedness and forming the slits such that they are generally
helical and have a second handedness opposed to the first
handedness.
9. The method as claimed in claim 7, further comprising forming the
helical thread portion to have right handed pitch the slits have
left handed pitch.
10. The method as claimed in claim 7, further comprising forming
the generally helical slits to further include sigmoid curves.
11. The method as claimed in claim 10, further comprising forming
the sigmoid curves to repeat along the length of the tubular
portion with a substantially regular periodicity.
12. The method as claimed in claim 7, further comprising
constructing the pattern geometry such that torsional displacement
is limited to a greater degree in a first rotational direction than
in a second rotational direction.
13. The method as claimed in claim 7, further comprising: forming a
helical thread portion at a distal end of the catheter that has a
first handedness and forming the slits such that they are generally
helical and have a second handedness opposed to the first
handedness; forming the generally helical slits to further include
sigmoid curves; forming the sigmoid curves to repeat along the
length of the tubular portion with a substantially regular
periodicity; and constructing the pattern geometry such that
torsional displacement is limited to a greater degree in a first
rotational direction than in a second rotational direction.
14. An intravascular catheter to be passed over a guidewire,
comprising: a screw portion defining a hollow lumen including a
cylindrical hollow shaft having a substantially constant first
diameter and a helical thread portion extending outwardly from the
hollow shaft; a tubular portion formed from a substantially rigid
material, having a length, joined substantially coaxially to the
screw portion and defining a lumen that is continuous with the
lumen of the screw portion, the tubular portion having a second
diameter substantially equal to the hollow shaft first diameter;
and a hub having a lumen joined substantially coaxially to the
tubular portion.
15. The catheter as claimed in claim 14, in which the tubular
portion defines along a portion of its length at least two slits
having a pattern geometry that limits torsional displacement of at
least a portion of the catheter, the at least two slits having a
first end and a second end, the first end and the second end being
longitudinally displaced from each other along the length of the
tubular substantially rigid structure.
16. The catheter as claimed in claim 15, in which the helical
thread portion has an outside diameter significantly larger than
the first diameter of the hollow shaft.
17. The catheter as claimed in claim 14, in which an outside
diameter of the helical thread portion is at least about one and
one third times the diameter of the first diameter of the hollow
shaft.
18. The catheter as claimed in claim 15, in which the helical
thread portion has a first handedness and the slits are generally
helical and have a second handedness opposed to the first
handedness.
19. The catheter as claimed in claim 18, in which the generally
helical slits further include sigmoid curves that repeat along the
length of the tubular portion with a substantially regular
periodicity; and further comprising a torque device couplable to
the tubular portion whereby torque can be applied to the tubular
portion; and an inner liner and an outer coating.
20. The catheter as claimed in claim 14, in which the tubular
portion has a diameter of about two French.
21. The catheter as claimed in claim 15, in which the pattern
geometry is such that torsional displacement is limited to a
greater degree in a first rotational direction than in a second
rotational direction.
22. The catheter as claimed in claim 14, in which the tubular
portion defines along a portion of its length at least two slits
having a pattern geometry that limits torsional displacement, the
at least two slits having a first end and a second end, the first
end and the second end being longitudinally displaced from each
other along the length of the tubular portion; in which the helical
thread portion has an outside diameter significantly larger then
the first diameter of the hollow shaft; in which the helical thread
portion has a first handedness and the slits are generally helical
and have a second handedness opposed to the first handedness; in
which the generally helical slits further include sigmoid curves
that repeat along the length of the tubular portion with a
substantially regular periodicity; in which the pattern geometry is
such that torsional displacement is limited to a greater degree in
a first rotational direction than in a second rotational direction;
in which the pattern geometry is such that torsional displacement
is limited to a greater degree in a first rotational direction than
in a second rotational direction; and further comprising a torque
device couplable to the tubular portion whereby torque can be
applied to the tubular portion; and an inner liner and an outer
coating.
Description
FIELD OF THE INVENTION
[0001] The invention relates generally to the field of
interventional cardiology devices. More particularly, the invention
relates to interventional cardiology devices to assist in passing a
stent or balloon through a vascular stenosis.
BACKGROUND OF THE INVENTION
[0002] There are many situations in which an interventional
cardiologist needs to pass an interventional cardiology device,
such as a stent or balloon, beyond a narrowing vascular lesion, or
vascular stenosis. Often, it is found that it is possible to pass a
guidewire through a stenotic or blocked artery but that the
stenosis or blockage prevents the passage of a larger device, such
as a balloon or stent carried by an intravascular catheter.
[0003] Previous approaches to this problem have often involved
attempts to increase the size of the available lumen. This approach
generally involves auger-like cardiology devices that seek to drill
or abrade their way through a stenotic lesion. This approach is
sometimes referred to as debulking the lesion. Examples of such
devices are found in U.S. Pat. Nos. 5,078,723, 5,968,064 and
6,666,874. Auger like devices tend to dislodge pieces of
atherosclerotic plaques. The dislodged pieces can be released into
the blood circulation and create emboli that may create circulatory
blockages downstream from the location of the initial stenosis.
[0004] Torsional displacement is one of the problems encountered
with previous approaches that can happen when applying torque or
torsional forces to intravascular catheters. Small diameter
intravascular catheters are typically less than two millimeters in
diameter and must be flexible to navigate the tortuous paths taken
by blood vessels within the body. Materials that allow the desired
flexibility tend to not transmit torque forces as well as is
desired. That is, the application of torque to a catheter would
ideally lead to rotation of the entire catheter about its long
axis; however, intravascular catheters made of flexible materials
tend to deform under torque loads instead of transmitting the
torque force consistently along their length. Depending on the
amount of torque applied smoothly at one end of a catheter that
torsional force may be transmitted unevenly at the opposing end of
the catheter. Thus, a smooth turning at one end may lead to a jerky
rotational motion at the other end as torque force is alternately
transmitted and stored by torsional displacement of the catheter
tube. In a severe case, this may lead to kinking of the tubular
portion of the catheter.
[0005] It would be desirable to have a catheter that could transmit
torque forces evenly along the longitudinal axis of the catheter
and with minimal torsional displacement of the catheter while still
having enough flexibility to navigate tortuous blood vessels.
[0006] It would also be desirable to provide a device that would
permit the passage of interventional cardiology devices larger than
a guidewire beyond stenotic lesions without dislodging emboli that
may create other complications.
SUMMARY OF THE INVENTION
[0007] In one embodiment, the present invention includes a small
diameter intravascular catheter made of metal or another rigid
material that includes a threaded tip with threads protruding
outwardly that exceed the diameter of the catheter tube. The
threaded portion of the catheter of the present invention is
utilized to engage and pull through the lesion rather than to auger
or abrade out material in the lesion. The catheter of one
embodiment of the present invention also includes a wall pierced by
slits that wind helically around the catheter. In one embodiment of
the invention, the slits have a pattern geometry that limits
torsional displacement and may include areas of sigmoid curves
periodically spaced along the longitudinal length of the slit
portion of the catheter having the slits.
[0008] The catheter of the present invention may also include an
inner polyimide or Teflon liner. In addition, the catheter of the
present invention may include an external polyurethane coating. In
one embodiment the catheter of the present invention may also
include a hub of a luer lock type. In one aspect of this
embodiment, a strain relief may be provided such as by a heat
shrink tubing at the juncture between the hub and the catheter.
[0009] The present invention may also include a torque device which
can be fastened to the catheter in order to provide for application
of torque to the catheter and thus to the screw. The screw portion
of the catheter of one embodiment the present invention defines an
interior lumen which is contiguous with lumen of the tubular
structure.
[0010] The intravascular catheter of one embodiment of the present
invention has enhanced flexibility in the distal-most 20-40
centimeters provided by laser cutting of a pattern geometry in the
tubular material of the catheter. The catheter may be formed from a
metallic hypotube. The hypotube may be formed, for example from
Nitinol or stainless steel. The pattern geometry allows flexibility
by using a helical pattern but also provides a pattern geometry
that limits torsional displacement when torque is applied to the
tubular portion of the catheter.
[0011] In another aspect of the invention, the tip of the catheter
has a helical thread pattern which is larger in diameter than the
tubular portion. For example, the threaded portion of the tip of
the catheter may be about 1.5 times larger in diameter as measured
at the outside of the threaded portion.
[0012] As the catheter of the present invention is passed through a
stenotic lesion it creates a plastic deformation of the lesion with
scoring lines created by passage of the screw threads. It is
notable that the lesion is not broken up, debulked or drilled out
but deformed toward the walls of the blood vessel.
[0013] For the purposes of this application, intravascular
catheters are generally considered to be those having a diameter
less than or equal to about twelve French. More likely they have a
diameter less than six French. Small diameter intravascular
catheters are those having a diameter of about three French or
less.
[0014] The application of torque or torsional forces to the
catheter varies between when the catheter is being manipulated
through the vasculature and when the screw portion of the catheter
is brought into contact with a lesion. When the catheter is being
passed through the often tortuous vasculature there is minimal
resistive torque encountered overall and particularly little
resistive torque that arises from the screw tip. Resistive torque
arises primarily from incidental contact between the catheter and
the walls of the blood vessel.
[0015] When the screw tip portion is brought into contact with the
lesion and the screw tip is being advance through the lesion
resistive torque arises in large measure from the lesion resisting
passage of the screw tip portion as the material of the stenotic
lesion is plastically deformed and displaced by passage of the
screw tip.
[0016] Once the stenotic lesion has been plastically deformed the
resistive torque that is encountered in removing the screw tip from
the lesion by reversing the rotation of the catheter is
considerably less than that required to advance the screw tip
through the lesion. Thus, the pattern geometry of the slits in the
tubular portion is such that it is preferably biased to being more
resistant to torsional displacement when the screw tip is being
advanced through the lesion than when the screw tip is being
withdrawn from the lesion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a plan view of a catheter in accordance with the
present invention.
[0018] FIG. 2 is a sectional view of a hub joined to a tube portion
taken along section line 2-2 of FIG. 1.
[0019] FIG. 3 is a detail plan view of a screw tip and part of a
tube portion taken from FIG. 1.
[0020] FIG. 4 is a cross-sectional view taken along section line
4-4 of FIG. 3.
[0021] FIG. 5 is a schematic sectional view of a catheter in
accordance with the present invention in situ in blood vessel that
has a stenotic lesion.
[0022] FIG. 6 is a detailed schematic sectional view of a catheter
in accordance with the present invention in situ in blood vessel
that has a stenotic lesion.
DETAILED DESCRIPTION OF THE DRAWINGS
[0023] Catheter 10, of one embodiment of the present invention,
generally includes screw portion 12, tube portion 14, hub 16,
strain relief 18, and torque device 20. Referring to FIG. 1, in one
aspect of the invention, screw portion 12 is located distally
followed by tube portion 14 and hub 16 located proximally. Strain
relief 18 may be located generally at the juncture of tube portion
14 and hub 16. In one embodiment of the invention, torque device 20
may be located along the length of tube portion 14 or at hub
16.
[0024] Referring particularly to FIGS. 3 and 4, depicting an
embodiment of the invention, screw portion 12 generally includes
hollow shaft 22 and helical thread 24. Screw portion 12 may be
formed from a rigid biocompatible material, for example, 304
stainless steel. Screw portion 12 may be gold plated or coated with
another biologically inert material or formed entirely from a
biocompatible material. Hollow shaft 22 defines screw lumen 26.
Hollow shaft 22 defines smaller diameter portion 28 of screw lumen
26 and larger diameter portion 30 of screw lumen 26. Hollow shaft
22 may have an outside diameter, for example, of about two French
or approximately 0.66 millimeters. It is notable that helical
thread 24 extends outwardly from hollow shaft 22 and has an outer
diameter somewhat larger than hollow shaft 22. Hollow shaft 22 is
of a similar diameter as tube portion 14 and, in one aspect of the
invention is generally cylindrical. For example, helical thread 24
of the tip of the catheter 10 may be about 1.5 times larger in
diameter as measured at the outside of the helical thread 24. For
example, helical thread 24 may have a diameter of about three
French, approximately one and one half times the diameter of hollow
shaft 22. The diameter of hollow shaft 22 may be substantially
equal to the diameter of tube portion 14, which may be about two
French.
[0025] Tube portion 14 may be formed from a rigid biocompatible
material. In one aspect of the invention, tube portion 14 may be
formed from metal. In another aspect of the invention, tube portion
14 may be formed from 304 stainless steel hypotube having an
outside diameter of approximately two French. Titanium or other
known metallic materials may also be used.
[0026] In one aspect of the invention, tube portion 14 includes
solid portion 32 and helically cut portion 34. In one embodiment of
the invention, helically cut portion 34 extends along approximately
the distal twenty five centimeters of tube portion 14 ending
shortly before the junction of tube portion 14 with screw portion
12. Helically cut portion 34 may be formed, for example, by laser
cutting. Helically cut portion 34 may also be formed by other
techniques known to the art such as etching or machining. Helically
cut portion 34 may include, for example, four helices 36.
[0027] Each of helices 36 may include sigmoid curve 38. Sigmoid
curves 38 may repeat along the length of tube portion 14 with a
generally regular periodicity or an irregular periodicity. Tube
portion 14 may be joined to screw portion 14 by the use of laser
welding techniques or adhesive techniques, for example.
[0028] In one aspect of the invention, hub 16 is located at the
proximal end of catheter 10. Hub 16 may be, for example, a standard
female luer adapter. Hub 16 may be formed of metal or a polymer
material. Hub 16 is fixedly joined to solid portion 32 of tube
portion 14. Hub 16 defines hub lumen 40 inside thereof. Hub lumen
40 may include entry taper 42, large lumen portion 44, tapered
funnel 46, and small lumen portion 48. Small lumen portion 48 has
an inside diameter similar to that of tube portion 14 and hollow
shaft 22.
[0029] The interior of tube portion 14, as well as small lumen
portion 48 of hub 16 and larger diameter portion 30 of screw
portion 12, may be lined by liner 50. Liner 50 may be formed of
polyimide and Teflon, in one embodiment of the invention. Other
liner materials may be used as well. The exterior of tube portion
14 may be coated with a polymer coating such as polyurethane.
[0030] Strain relief 18 may cover the proximal portion of tube
portion 14. Strain relief 18 may be formed of a heat shrink wrap
tubing.
[0031] Referring again to FIG. 1, in one aspect of the invention,
torque device 20 may be removably attachable or permanently
attached to tube portion 14. Torque device 20 is dimensioned to
allow easy hand gripping by a physician using catheter 10. Torque
device 20 may be adjustable and positioned along the length of tube
portion 14. Torque device 20 may also be secured to hub 16.
[0032] Referring to FIGS. 5 and 6, catheter 10 is intended to be
inserted over guidewire 52 after guidewire 52 has been passed at
least partially through a lesion in the vasculature. FIGS. 5 and 6
depict guidewire 52 partially inserted through stenotic lesion 54.
Guidewire 52 is inserted into lesion prior to placement of catheter
10. Guidewire 52 may be inserted partially or completely through
stenotic lesion 54 before catheter is inserted over guidewire
52.
[0033] In operation, catheter 10 is inserted into a large blood
vessel over a preplaced guidewire 52 which has been passed at least
partially through a stenosis. When catheter 10 is inserted over the
guidewire 52, the guidewire 52 has already been passed through a
stenosis or blockage in a blood vessel. Screw portion 12 is brought
into abutment with stenotic lesion 54 pierced or transited by
guidewire 52. An operator of catheter then grasps torque device 20
and turns catheter 10 by turning torque device 20.
[0034] Torque device 20 transfers rotational motion to solid
portion 32 of tube portion 14. The turning of solid portion 32
applies torque to helically cut portion 34. The presence of sigmoid
curves 38 locks helices 36 such that torque may be applied to screw
portion 14 where it abuts the stenotic lesion 54. Helices 36 lock
helically cut portion 34 such that helically cut portion 34 can
transmit torque forces without excessive "winding up" helically cut
portion 34.
[0035] Referring to FIGS. 5 and 6, helical thread 24 engages to the
stenotic lesion 54. The engagement of helical thread 24 with lesion
54 forces the opening made by the guidewire in lesion 54 to expand
by plastic deformation and displacement of lesion 54 material. It
is notable that helical thread 24 does not auger, abrade or
otherwise remove material from lesion 54. Screw portion 12
plastically deforms the material of lesion 54 to displace it and to
create a larger passageway for an interventional cardiology device
to pass through without removing material from lesion 54. In
addition, catheter 10 is drawn forward through lesion 54 taking
along with it any interventional cardiology device attached
thereto.
[0036] As it passes through stenotic lesion 54, helical thread 24
scores interior surfaces of stenotic lesion 54 creating a smoother
lumen therethrough than previously existed. In addition, helical
thread 24 leaves a scored impression on the walls of lesion 54.
This may have the beneficial effect of reducing turbulence within
the narrowed lumen created by stenotic lesion 54 by improving
laminar flow along the lumen walls thus decreasing the risk of
embolus formation at lesion 54.
[0037] The foregoing description of an exemplary embodiment of the
invention has been presented for the purpose of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise form disclosed. Many modifications and
variations are possible in light of the above teaching. It is
intended that the scope of the invention not be limited with this
detailed description, but rather by the claims appended hereto.
* * * * *